Michael Laudrup's defensive problems could be set to increase with Ashley Williams a doubt for Swansea's Barclays Premier League meeting with Everton.

The Welsh club are already without Neil Taylor (broken ankle), Kyle Bartley (thigh), Chico Flores (suspension) and Garry Monk (back), with Alan Tate and Ben Davies coming into the side for the defeat at Aston Villa.

But Wales international Williams is struggling with an ankle problem and midfielder Kemy Agustien, who would have been a candidate to replace the centre-half, has been ruled out with a calf injury.

Williams has had a difficult few weeks. Uncharacteristic errors from the 26-year-old cost Swansea goals against Villa and Sunderland, while he was part of the Wales side humbled 6-1 by Serbia. But Laudrup insists he remains a key figure for the Swans and is desperately hoping he comes through a fitness test.

"He has had a difficult week and has not been able to do much because of his ankle, but he will hopefully be fit. It is important for us that our captain is there," Laudrup said.

"He had made mistakes but players are allowed to make mistakes and are permitted to have bad games because the important thing is that they give their all and they play in the way we want them to. Mistakes can happen."

Laudrup may also make changes in midfield with record signing Pablo Hernandez and Ki Sung-yueng pushing for their first starts for the club.

Moving Spain international Hernandez into the side at the expense of Wayne Routledge or Nathan Dyer would be harsh on the pair, who have excelled during Swansea's bright start to the campaign.

Everton have made a good start to the season themselves, with their draw against Newcastle leaving them level on points with the fifth-placed Swans.

"It is a big challenge for us against a club who have a lot of continuity on the pitch and off the pitch," Laudrup said. "David Moyes has been there 10 years so everyone knows exactly what is wanted of them. They are strong with a lot of individual quality, especially on the left side where they are very good with Leighton Baines and Steven Pienaar."